The present invention relates to a display unit such as a CRT (Cathode Ray Tube) for a word processor and, more specifically to a CRT display unit capable of multi-frame displaying.
While editing a document by a word processor, you may need to change the format or recall other sentences that have been already registered. To provide for these requirements, a need exists for display device that can change the display mode temporarily to replace the present picture with another one.
If the present picture has been entirely replaced, however, it becomes impossible to know the relationship between the former data and the new data. In this sense, it is desirable for the display device to present a plurality of pictures simultaneously in one frame. A multi-picture display called a multi-window has been introduced for this purpose. With the multi-window method, other pictures for temporary reference are shown in windows overlapping with the existing picture.
According to the conventional multi-window method, the window is shown on or overlapping the existing picture regardless of the position of the cursor, thus interfering with any editing input operations.